ACPAtmospheric Chemistry and PhysicsACPAtmos. Chem. Phys.1680-7324Copernicus GmbHGöttingen, Germany10.5194/acp-12-7215-2012Diel cycles of isoprenoids in the emissions of Norway spruce, four Scots pine chemotypes, and in Boreal forest ambient air during HUMPPA-COPEC-2010YassaaN.12SongW.1LelieveldJ.1VanhataloA.3BäckJ.3WilliamsJ.11Department of Air Chemistry, Max-Planck Institute for Chemistry, Mainz, Germany2USTHB, University of Sciences and Technology Houari Boumediene, Faculty of Chemistry, BP 32 El-Alia Bab-Ezzouar, 16111 Algiers, Algeria3Department of Forest Sciences, University of Helsinki, Finland07082012121572157229This work is licensed under a Creative Commons Attribution 3.0 Unported License. To view a copy of this license, visit http://creativecommons.org/licenses/by/3.0/This article is available from http://www.atmos-chem-phys.net/12/7215/2012/acp-12-7215-2012.htmlThe full text article is available as a PDF file from http://www.atmos-chem-phys.net/12/7215/2012/acp-12-7215-2012.pdf

Branch enclosure based emission rates of monoterpenes and sesquiterpenes from
four Scots pines (<i>Pinus sylvestris</i>) and one Norway spruce
(<i>Picea abies</i>), as well as the ambient mixing ratios of monoterpenes
were determined during the HUMPPA-COPEC 2010 summer campaign. Differences in
chemical composition and in emission strength were observed between the
different trees, which confirmed that they represented different chemotypes.
The chemotypes of Scots pine can be classified according to species with
high, no and intermediate content of Δ-3-carene. The
"non-Δ-3-carene" chemotype was found to be the strongest emitter of
monoterpenes. From this chemotype, β-myrcene, a very reactive
monoterpene, was the dominant species accounting for more than 32 % of the
total emission rates of isoprenoids followed by β-phellandrene
(~27%). Myrcene fluxes ranged from 0.8 to
24 μg g<sup>−1</sup> (dw) h<sup>−1</sup>. α-Farnesene was the
dominant sesquiterpene species, with average emission rates of
318 ng g<sup>−1</sup> (dw) h<sup>−1</sup>. In the high Δ-3-carene chemotype,
more than 48% of the total monoterpene emission was Δ-3-carene. The
average Δ-3-carene emission rate (from chemotype 3), circa
609 ng g<sup>−1</sup> (dw) h<sup>−1</sup> reported here is consistent with the
previously reported summer season value. Daily maximum temperatures varied
between 20 and 35 °C during the measurements. The monoterpene
emissions from spruce were dominated by limonene (35%),
β-phellandrene (15%), α-pinene (14%) and eucalyptol
(9%). Total spruce monoterpene emissions ranged from 0.55 up to
12.2 μg g<sup>−1</sup> (dw) h<sup>−1</sup>. Overall the total terpene flux
(monoterpenes + sesquiterpenes) from all studied tree species varied from
230 ng g<sup>−1</sup> (dw) h<sup>−1</sup> up to
66 μg g<sup>−1</sup> (dw) h<sup>−1</sup>. Total ambient monoterpenes
(including α-pinene, Δ-3-carene, β-pinene and
β-myrcene) measured during the campaign varied in mixing ratio from a
few pptv to over one ppbv. The most abundant biogenic VOC measured above
the canopy were α-pinene and Δ-3-carene, and these two
compounds together contributed more than 50% of the total monoterpenes.
The ambient data reflect the emission rate, atmospheric reactivity and tree
type abundance. The diel cycles of isoprenoid mixing ratios showed high
levels during the night-time which is consistent with continued low nocturnal
emission and a low and stable boundary layer. The chirality of
α-pinene was dominated by (+)-enantiomers both in the direct emission
and in the atmosphere. The two highest emitters showed no enantiomeric
preference for α-pinene emissions, whereas the two lowest emitting
pines emitted more (+)-enantiomer. The spruce emissions were dominated by
(−)-enantiomer. The exceptionally hot temperatures in the summer of 2010
led to relatively strong emissions of monoterpenes, greater diversity in
chemical composition and high ambient mixing ratios.